The invention relates to a gear shifting mechanism of the type which includes a shift stick extending into the passenger compartment of the vehicle for manual operation by the driver. More particularly, the invention relates to an arrangement for preventing vibration generated in the engine and drive train from being transmitted to the passenger compartment through the shift stick.
Experience has shown that one source of noise in cars having stick shift transmissions is the conduction of noise and vibration from the transmission and engine through the shifting mechanism and the shift stick into the passenger compartment of the vehicle. The noise and vibration thus transmitted may cause the shift stick to vibrate, to generate an audible hum, or both.
In the prior art, stick shifters were provided with a socket or the like, for receiving the shift stick, the socket having a sound insulating lining for isolating the shift stick from the vehicle drive train. However, mounting the shifter stick or handle in an elastomer vibration isolation material results in a shifting mechanism having a poor feel. Also, since the mass of the suspended stick shift is quite low, the natural frequency of the shift stick is relatively high. This is undesirable since it is known that the natural frequency of a supported structure must be small in comparison to the frequency of the disturbing force for the isolator to perform its function, substantially reducing the transmissibility of the disturbing force to the supported structure. The expense of providing a socket lined with a vibration isolating material also renders this an undesirable arrangement for isolating the stick shift from drive train vibration.
Elastomer bushings have been used in prior art for interconnecting two relatively movable parts without transmitting vibration from one part to another. For example, such bushings are found in automotive transmission and steering linkages. Such bushings have also been used as engine mounts for isolating engine vibration from a vehicle body and as shock mounts for various structures mounted on a vehicle.